A wide variety of illuminated electronic displays are currently in common use. Perhaps the most familiar of such displays are cathode ray tubes (CRT's). CRT's are popular because they have many advantages. They produce bright, high resolution, color images. They do, however, have significant disadvantages in certain situations. Compared with alternatives such as liquid crystal displays (LCD's) and electroluminescent displays (ELD's) they are bulky and consume large quantities of power. In contrast, LCD's are much thinner and consume much less power. This makes LCD's preferable for applications where space or energy consumption is important. Examples of applications where such considerations are important are lap-top computers, where both energy consumption and space are critical, and automobile dashboard displays, where the volume is of particular importance.
Because LCD's are not light emitting, they require a light source. Although they may use ambient light, an internal light source typically placed behind the display usually provides greater readability, especially in a dark environment. As a result, there is a minimum thickness necessitated by the illumination source.
An alternative type of display is electroluminescent. In an electroluminescent display, electroluminescent materials may be used as a light source for another type of display, such as an LCD, or may be both the light source and the display itself. Electroluminescent displays have the advantage of being thin, cool, and highly efficient. One problem with electroluminescent displays, however, is a lack of brightness. This is often overcome by increasing the voltage applied to the electroluminescent material. While this will increase the brightness of the display, it reduces the display's reliability and lifetime.
A second problem with electroluminescent displays is that they are inherently grainy in appearance. This graininess reduces readability and increases operator fatigue especially when such displays are used for extended periods of time. The increase of voltage that will produce brighter intensity still does little or nothing to overcome the problem of the grainy appearance.